1. Field of the Invention
This invention relates to four-component wide angle zoom lenses, particularly of the type whose shortest focal lengths are shorter than the length of the diagonal of the image size, which exhibit a zoom ratio larger than 2.5, and which start with a convergent lens group.
2. Description of the Prior Art
A wide variety of zoom lenses of the convergent component-preceded four-component type are known. They are shown, for example, in Austrian patent specifications filed Nov. 18, 1974 Application No. A9242/74, and filed Aug. 11, 1975, Application No. A6230/75, Japanese Pat. Publication Nos. Sho 53-9095 and Sho 40-13314, and Japanese Laid-Open Pat. Nos. Sho 52-104137 and Sho 52-69640.
With such convergent component-preceded four-component zoom lenses, achieving compactness requires avoiding a large increase in the diameter of the front component by making the focal length of each of the zoom components as small as possible. However, as the focal length of each of the zoom components is reduced, zooming causes variations of the aberrations and, in particular, makes distortion, astigmatism, and aspherical aberration very prominent. Thus, it is difficult to obtain a properly corrected wide angle zoom lens of this type. Also, though a divergent component-preceded or so-called two-component zoom arrangement is generally more advantageous than a convergent component-preceded four-component zoom type for correcting aberrations in the wide angle positions and shortening the diameter of the front members, when the zoom ratio is increased to as high as 2.5 or more, it becomes very difficult to obtain good aberration correction stability in the telephoto position and to achieve a large increase in the relative aperture.